Chem_340_Key_Quiz_2_Spring_2012

Chem_340_Key_Quiz_2_ - ∆ U is positive because the temperature increases an some of the liquid is vaporized 3(3 points One mole of an ideal gas

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CHEM 340: Physical Chemistry for Biochemists I, Spring 2012 February 3, 2012 Quiz 2 Print Your Name:_________________________________________________ 1. (2 points) 3.00 moles of an ideal gas are compressed isothermally from 60.0 to 20.0 L using a constant external pressure of 5.00 atm. Calculate q, w, U, and H. The work against a constant pressure: () ( ) J 10 03 . 2 m 10 20 m 10 60 Pa 101325 5 V p w 4 3 3 3 3 external × = × × × × = = 0 U = and 0 H = since 0 T = J 10 03 . 2 w q 4 × = = 2. (2 points) A cup of water at 278 K (the system) is placed in a microwave oven and the oven is turned on for 1 minute during which it begins to boil. Which of q, w, and U are positive, negative, or zero? The heat, q, is positive since heat flows across the system-surrounding boundary into the system. The work, w, is negative because the vaporized water does work on the surroundings.
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Unformatted text preview: ∆ U is positive because the temperature increases an some of the liquid is vaporized. 3. (3 points) One mole of an ideal gas for which C V,m = 20.8 J K –1 mol –1 is heated from an initial temperature of 0.00°C to a final temperature of 275°C at constant volume. Calculate q, w, ∆ U, and ∆ H for this process. For a process with V = constant: w = 0 ( ) ( ) ( ) kJ 5.72 J 5720.0 mol 1.0 K 275 mol K J 20.8 ∆ T C ∆ U q 1 1 V = = × × = = = − − ( ) ( ) ( ) ( ) ( ) ( ) ( ) kJ 8.0 J 8006.0 K 273 mol 1.0 mol K J 20.8 mol 1.0 mol K J 8.314472 ∆ T C R n ∆ T C ∆ H 1 1 1 1 V p = = × × + × = + = = − − − −...
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This note was uploaded on 04/07/2012 for the course CHEM 340 taught by Professor Staff during the Spring '08 term at Ill. Chicago.

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